Research On Constrained Attitude Control For Rigid Spacecraft

The spacecraft technology plays an important role in the military and civil application,and the attitude control is one of the key problems in spacecraft control.The spacecraft is a nonlinear coupled multi-input multi-output complex system.The spacecraft attitude control models based on the quaternion and modified Rodrigues parameter are constructed in this thesis,such that the complex calculations and gimbal lock problem of the Euler angles is avoided.For the rigid spacecraft with inertia uncertainty,external disturbance,input constraint including actuator saturation and faults,a modified barrier Lyapunov function(MBLF)is constructed to extend the application scope of the traditional logarithmic barrier Lyapunov function.Then,the attitude constrained controllers are designed by combining the sliding mode control,MBLF and backstepping to ensure the high-precision control and transient performance for the rigid spacecraft.The main research contents of this thesis are summarized as follows:1.A fast power reaching law based sliding mode control with disturbance observer is presented to solve the attitude tracking control problem for the rigid spacecraft with the existence of inertia uncertainty and external disturbance.A disturbance observer is presented to estimate the lumped disturbance with bounded change rate.Then,a sliding mode controller is designed based on the fast power reaching law with considering disturbance estimation to ensure the convergence of the attitude and angular velocity tracking errors.Lyapunov theorem is given to verify the stability of the closed-loop system.2.A barrier Lyapunov function(BLF)based backstepping control design is proposed for uncertain rigid spacecraft with actuator saturation and faults.A modified barrier Lyapunov function(MBLF)is constructed to extend the application scope of the traditional logarithmic barrier Lyapunov function.Through using the modified barrier Lyapunov functions in each step of the backstepping design,an adaptive constrained control scheme is presented to guarantee the tracking performance and the constraint requirement of spacecraft systems,and the differentiation of the virtual control is avoided with the employment of the tracking differentiator(TD).The uncertainty bounds are estimated by designing adaptive update laws,such that no prior knowledge is required on the bound of the lumped uncertainty including input saturation and faults.3.A full state constrained output feedback control scheme is proposed for the rigid spacecraft with actuator saturation and without angular velocity measurement.The system model is constructed based on the modified Rodrigues parameter description,and the asymmetric modified barrier Lyapunov function(AMBLF)is presented.A second order auxiliary system is constructed,with the error between the control input and saturation input as the input of the constructed system,and signals are generated to compensate the effect of saturation.Then,a state observer is designed to estimate unknown system states,and the output feedback control law is designed by using backstepping techniques to ensure the full state constraints and attitude tracking accuracy.Through the Lyapunov stability analysis,the state observation errors and tracking errors are proved to be uniformly ultimately bounded.4.An adaptive finite-time fault-tolerant control scheme is proposed for the attitude stabilization of rigid spacecraft with inertia uncertainty,external disturbance,actuator saturation and faults.A first-order command filter is presented at the second step of the backstepping design to approximate the derivative of the virtual control,such that the singularity problem caused by the differentiation of the virtual control is avoided.Then,a fuzzy logic system is designed to estimate the system uncertainties.Through using an error transformation,the prescribed performance boundary is incorporated into the controller design to guarantee the prescribed performance of the system output.The adaptive fuzzy finite-time backstepping controller is developed to achieve the finite-time spacecraft attitude stabilization.5.The numerical simulations demonstrate the effectiveness and superiority of the proposed control schemes.Finally,the main research results of this thesis are summarized and the future research proposals are suggested.